Press brakes are commonly used to bend or otherwise deform sheet-like workpieces, such as sheet metal. A conventional press brake has an upper beam and a lower beam, at least one of which is movable toward and away from the other. Typically, the upper beam is movable vertically while the lower beam is fixed in a stationary position. It is common for a male forming punch and a female forming die to be mounted respectively on the upper and lower beams of a press brake.
Typically, the punch has a downwardly-oriented, workpiece-deforming surface (or “tip”). The configuration of this surface is dictated by the shape into which it is desired to deform a workpiece. The die typically has a recess, bounded by one or more workpiece-deforming surfaces, that is aligned with the tip of the punch. The configuration of this recess corresponds to the configuration of the punch's tip. Thus, when the beams are brought together, a workpiece between them is pressed by the punch into the die to give the workpiece a desired deformation (e.g., a desired bend).
From time to time, it is necessary to exchange punches and dies to accommodate different bending operations. The manner in which punches and dies are mounted on, and dismounted from, a press brake depends upon the particular style of tool holder/tooling being used. In some cases, the tool holder has a clamp that can be actuated to close securely upon (i.e., to clamp on) the tang of a press brake tool. In many cases, the clamp holds the tool's tang against a horizontally elongated wall (or “bed”) of the upper or lower beam. When the clamp is loosened, the tool can be removed. In certain instances, the tool can be removed by moving it vertically out of the clamp. In other instances, the tool must be removed by sliding it horizontally out of the clamp.
Many press brake tool holders have been devised. Some employ clamps that are actuated mechanically. Others employ clamps that are actuated hydraulically. Exemplary tool holders of both types will now be described.
U.S. Pat. No. 4,993,255 (issued to Treillet), the entire contents of which are incorporated herein by reference, discloses a tool holder that is attached by means of a C clamp to the bed of the upper table. Through use of a camming mechanism, the upwardly extending shank of a tool is captured between a pivotable clamp and a portion of the holder, the shank and clamp having cooperating surfaces enabling the tool to be readily inserted in the holder. In this patent, a locking cam is disclosed for locking the clamp against the tool.
U.S. Pat. Nos. 5,513,514, 5,511,407, and 5,572,902 (each issued to Kawano), and European patent publication 0 644 002 A2, the entire contents of each of which are incorporated herein by reference, all show tool holders in which a pivoting clamp is employed to secure the shank of a tool against the mounting plate of a tool holder. In each of these patents, the tool holder is equipped with a threaded mechanism operated by a lever that pivots from side to side to lock and unlock the clamp, force being transmitted from the lever to the clamp via a spring structure.
U.S. Pat. No. 6,003,360 (issued to Runk et al.), the entire contents of which are incorporated herein by reference, provides a particularly advantageous press brake tool holder. The tool holder includes a clamp that opens to a position allowing manual removal of the tool while preventing the tool from falling. The clamp in certain preferred embodiments is actuated with a manual lever.
U.S. Pat. No. 6,151,951 (issued to Kawano), the entire contents of which are incorporated herein by reference, discloses a tool holder having multiple hydraulically actuated pistons that transmit force generated by hydraulic fluid to a clamp. The pistons are displaced outwardly to force the clamp shut.
U.S. Pat. No. 6,564,611 (issued to Harrington et al.), the entire contents of which are incorporated herein by reference, discloses particularly advantageous hydraulic press brake tool holders. The press brake tool holders are configured for releasing and securing press brake tools in response to applied fluid pressure. One disclosed tool holder includes a horizontally-elongated body having a cam shaft bore disposed longitudinally therethrough, and receiving a slidably and sealingly mounted cam shaft therein. The cam shaft can have at least one axial camming surface, having a large outer diameter region axially tapered to a small outer diameter region, and in contact with a cam follower pin slidably disposed in a cam follower pin bore transversely disposed through the body. The cam follower pin can bear against a pivotally mounted clamp disposed about the body. In response to applied fluid pressure, the camming surface can slide axially, thereby increasing the effective outer diameter as seen by the cam follower pin, urging the cam follower pin outward and against the upper portion of the pivotally mounted clamp, and closing the lower clamp portion about a press brake tool.
Insofar as mechanically-actuated tool holders are concerned, a press brake operator generally moves a handle of the tool holder manually to actuate the clamp. While tool holders of this nature are entirely acceptable in most cases, it would be desirable to provide a tool holder in which clamping and unclamping can be performed without requiring an operator to manually move a handle.
Hydraulic tool holders also have limitations. For example, hydraulic tool holders may require cumbersome hydraulic hoses, expensive hydraulic power supplies, and control valves. Such bulky hydraulics tend to render hydraulic clamps difficult to use. Moreover, these clamps tend to have hydraulic fluid leaks, which can contaminate cutting fluids as well as the environment. Hydraulic clamps also tend to have relatively high maintenance costs and relatively high noise levels.
Pneumatic clamps would also have shortcomings. For example, pneumatic clamps would tend to have high noise levels. Pneumatic systems may also release oil mist into the air, creating a “shop air” smell. Further, pneumatic systems tend to require expensive compressors, filter/regulator packages, and maintenance. Moreover, pneumatic clamps may be limited in terms of clamping force.
Finally, in certain automated machining processes, it may be desirable to move a tool holder among one or more machining stations. This type of movement would tend to be cumbersome with hydraulic or pneumatic systems.
The present invention provides a new and improved press brake tool holder, which overcomes the above-noted problems and others.